The utilization of magnetic tape recorders, particularly those using magnetic tape cartridges or cassettes has burgeoned in recent years with a resultant increase in the number of cassettes. The fact that automobiles are now often equipped with cassette players has further increased the use of cassettes. Such cassettes are often supplied in a case which serves as a dust cover and which is usually fitted with some mechanism for restraining the rotation of the sprockets. The case provides a protective function and it is desirable that the cassette be stored in the case between uses. Not only does the case protect the cassette from dust and mechanical abuse, but by restraining the movement of the sprockets, prevents the tape from accidentally unwinding. In the absence of restraint, when the tape is transported from one place to the other, or is placed in the groove compartment of a moving car, jostling of the cassette can result in unwinding of the sprocket with consequent loosening of the tape so that when it is played, the sudden tightening of the inner spool on its sprocket could result in tearing of the tape.
A drawback to the usual magnetic tape cassette case is that it is substantially bulkier than the cassette itself. This results partially from the fact that the cassette case must be deep enough to accomodate the thickest portion of the cassette, i.e., the trapezoidally shaped boss adjacent the open tape transport region of the cassette, and additionally includes some mechanism to make the tape readily and easily removable, usually taking the form of a pivot tray within the case itself. Add to this the usual practice of storing, with the cassette, information about the cassette and its contents and the result is a package which is substantially bulkier than the cassette. Since the cassette itself is usually labeled to contain most of the information packaged in the case that is of interest to the purchaser, oftentimes the purchaser will simply discard the case choosing to store the cassettes alone. Consequently, the cassettes suffer the dangers which the case was intended to avoid, simply because of the bulk of the case and the inconvenience of storing the cassette in the case.
The present invention provides a means for overcoming the foregoing problems by providing a shield for a magnetic tape cassette which is very readily and easily applied to the cassette yet which does not add to the total thickness dimension of the cassette. In particular, the shield comprises, integrally, an apron formed with an opening for receiving the shaped boss adjacent the open tape transport region of the cassette, a ledge which projects substantially at right angles from the inner surface of the apron for covering the open tape transport region, and means for securing the apron to a surface of the cassette. Additionally, the cassette can be provided with keeper means extending from the inner surface of the apron for engaging at least one of the sprocket holes to restrain the sprocket therein from turning. The keeper means can comprise prongs placed along the length of the apron.
The apron is preferably of a thickness which approximates the distance the boss is raised from the cassette surface. In keeping with the shape of the cassette boss, the opening is in the form of an isosceles trapezoid for matingly engaging the perimeter of the boss. The apron securing means preferably comprises a pair of nibs on the ledge adjacent an outer edge of the ledge, spaced from the apron a distance substantially the same as the thickness of the edge of the cassette. The nibs are aligned with the apron on opposite ends of the opening, so that each nib, the ledge and the apron, together, form in cross-section a U-shaped channel for receiving the cassette edge.
By forming the shield of transparent material, any label on the cassette can be readily perceived, the shield forming with the cassette a very compact unit permitting storage of a much larger number of cassettes than would be permitted were the cassettes themselves stored in cases, yet providing the mechanical and dust protecting advantages of the case.